Feynman Amplitude and Scattering Cross-Section for a Toy Theory
Amplitude and differential cross sections for two-body scattering are calculated using a second-order Feynman diagram of a toy theory (no spin, no charge, no polarization, no color) in the center of mass system. The graphs show the Feynman amplitude ℳ and the differential cross section dσ/dΩ as functions of the scattering angle θ, in radians. You can vary the mass of the exchanged virtual particle and see how the curves behave.[more]
The general relation between differential cross section and Feynman amplitude is: .[less]
 J. D. Griffiths, Introduction to Elementary Particles, Weinheim, Germany: Wiley-VCH Verlag GmbH, 2008. doi:10.1002/9783527618460.